The term "Retroviruses" refer to a family of viruses which contain RNA and which encode a reverse transcriptase (RNA-dependent DNA polymerase). The reverse transcriptase, which is capable of using the viral RNA as a template for the synthesis of complementary DNA, is essential to the first stage of the virus' self-replication.
Retroviruses include various oncoviruses such as avian leukemia virus, avian sarcoma virus, avian reticuloendotheliosis virus, murine mammary cancer virus, murine leukemia virus, murine sarcoma virus, guinea pig type C virus, hamster type C virus, rat leukemia virus, feline leukemia virus, feline sarcoma virus, feline type C virus, ovine leukemia virus, bovine leukemia virus, swine type C virus, simian leukemia virus, Mason-Pfizer virus, simian sarcoma virus, simian T-lymphotropic virus, baboon type C virus, and the like. Among those infective to human, important ones are adult T-cell leukemia virus (ATLV), or human T-lymphotropic virus type I (HTLV-I), and type II (HTLV-II). The adult T-cell leukemia abounds in Japan, especially in the west part, but the effective treatment containing prevention and therapeutics of the disease has not been established.
On the other hand, retroviruses also include those having no oncogenecity, such as visna virus, ovine progressive pneumonia virus, ovine maedi virus, simian T-lymphotropic virus type III (STLV-III), equine infectious anemia virus, and the like. The viruses isolated from human as causative agents for AIDS or ARC etc. (HTLV-III, LAV1, LAV2, ARV, and other so-called AIDS-viruses.) belong to this subfamily. Recently, AIDS-causative viruses have been termed HIVs (human immune deficiency viruses).
A third subfamily includes viruses such as a spumavirinae to which the simian foaming virus belongs. In addition, a retrovirus has recently been isolated as a causative virus for Kawasaki disease (mucocutaneous lymphonode syndrome).
World-wide interests have been focused on AIDS due to its unfavorable prognosis. It is a clinical syndrome characterized by recurrent oppotunistic infections, (e.g. pneumocystis carinii pneumonia, cryptococcal meningitis, disseminated toxoplasmosis), lymphadenopathy, and an aggressive Kaposi's sarcoma, and induces a high mortality more than 90% by the dysregulation of immune system. It is also known that the helper-T cells are specifically destroyed by the infection of the virus.
In order to find out pharmaceutical agents effective on the treatment of AIDS, ARC, PGL, and AIDS-virus carrier, the present inventors, using a cell line of MT-4 established from T-cells of adult T-cell leukemia patient and HTLV-III which is a causative virus for AIDS, examined the effects of various substances on the infection and replication of HTLV-III.
The above MV-4 cell line is absolutely susceptible to infection with HTLV-III. Infection followed by cell lysis (experimental HTLV-III infection). The present inventors have found that when certain polysaccharides having sulfonate group (--SO.sub.3 --) or mucopolysaccharides having sulfonate group or their additionally sulfuric acid esterified derivatives were added to the experimental HTLV-III infection system, the infection of HTLV-III on MT-4 cells and viral replication were strongly inhibited without any accompanying toxicity to the cells.
Further, the present inventors demonstrated that the above polymerized sugar inhibits the reverse transcriptase of the retrovirus in vitro, and thereby suppresses the replication of the virus.